Which factor primarily determines the contrast of a radiograph?

The factor that primarily determines the contrast of a radiograph is kVp, or kilovoltage peak. The kVp setting affects the penetration ability of the X-rays that are produced. A higher kVp results in X-rays that have greater energy and can penetrate tissues more effectively. This increased penetration leads to a broader range of densities on the radiograph, thus enhancing the contrast.

When kVp is set appropriately, the radiograph shows a greater variation between the different densities of the tissues or structures being imaged, allowing for better differentiation between them. On the other hand, if the kVp is too low, the image may appear flat with insufficient contrast, making it difficult to distinguish between various anatomical features.

While mA and exposure time contribute to the overall image quality and density, they do not primarily dictate the contrast level. Instead, they are more related to the quantity of X-ray photons produced and the duration of exposure, which are essential for producing adequate image brightness but do not significantly influence the contrast between different tissues in the radiograph.